System supporting animation of graphical display elements through animation object instances

ABSTRACT

A graphical display animation system is disclosed that supports timed modification of element property values of elements within a graphical display. The animation system utilizes a display structure for maintaining a set of elements corresponding to displayed objects within a graphically displayed scene. The elements include a variable property value. The animation system also utilizes a property system that maintains properties associated with elements maintained by the display structure. The properties include dynamic properties that are capable of changing over time—and thus affecting the appearance of the corresponding element on a graphical display. The animation system includes animation classes, from which animation objects are instantiated and associated with an element property at runtime. The animation object instances provide time varying values affecting values assigned to the dynamic properties maintained by the property system.

FIELD OF THE INVENTION

[0001] The present invention relates generally to computing devices.More particularly, the present invention relates to computing systemcomponents and sub-systems for maintaining and providing graphical userinterface views driven by data and instructional input from an operatingsystem and/or applications.

BACKGROUND OF THE INVENTION

[0002] Graphical user interfaces by their nature are highly visual. Atypical interactive session involving a user and a graphical userinterface includes multiple instances of a user performing an actionwith regard to a displayed element (e.g., moving a pointer and selectingan icon or control) to invoke an operation and then visually observingthe consequences of the operation. One way to draw a user's attention toparticular elements on a graphical user interface, to indicate an activeor changed status, is through animation of the graphical element.Animation, as used herein, includes changing the appearance or locationof a graphical display element (e.g., an icon, a control, a window,etc.) through a sequence of incremental changes applied to the displayelement over a period of time. However, animation also includestime-based changes to non-visually displayed elements. Thus, animation,as referred to herein, comprises both visual (i.e., changing a visualdisplay parameter value) and non-visual animation (i.e., changing aparameter value over time without affecting a visual display element).

[0003] Animation has the potential to enhance the usability andaesthetic appeal of computer systems and applications. User interfaces,and more particularly graphical user interfaces, occupy an importantrole in computer/user interactions. Animation enhances the computer/userinteraction experience by providing an additional type of information orway of conveying the status of a computer program, or component thereof,to the user. For example, rather than causing a selected item to merelydisappear or instantly change, animation enables a progression ofchanges to be displayed that, in combination with an understood context,informs a user what has occurred (e.g., a deleted file floating to arecycle bin). Furthermore, many would agree that animation makesinteraction with a computer system more interesting and engages theattention of users more effectively. Furthermore, animation can alsoautomate changes to property values. In particular a user-modeapplication sets up manual timers and then responding to those timers tochange a value.

[0004] Animation is likely not incorporated into many user interfaceswhere such animation would be beneficial to a user. One reason is simplythe cost of animating user interface elements. Animation is generally atime-consuming/cumbersome task. Taking a cost/benefit approach toimplementing animation in graphical user interfaces, the benefit ofincorporating animation should exceed its cost. Due to the currentrelatively high cost of animation programming, many applications thatwould benefit from animation are not animated because of its relativelyhigh implementation cost.

[0005] One way to reduce the cost of animation is to reuse animationprogramming for multiple distinct uses. However, animation code is notgenerally reused. Instead, single (application) use animation code isprogrammed completely within the applications themselves at developmenttime using programming tools. The animation behavior is definedexplicitly within the compiled program code. During runtime, theanimation is carried out by merely executing the previously programmedcode segment. In addition to being a time-consuming endeavor,incorporating animation into a program potentially results in an undulylarge program due to detailed data and instructions utilized to carryout the desired animation behaviors in display elements.

[0006] Efforts to enhance the programmability of animation in userinterfaces have resulted in the design and provision ofnon-editable/monolithic animation script sequences from which executablescript segments are referenced to provide a desired animation behavior.Such known animation programming methods, based for example upon theSynchronized Multimedia Integration Language (SMIL) standard,incorporate key-framing. The key-framing methods rely upon referencingparticular segments of monolithic, non-editable, animation scripts.

[0007] The prior known key-framing approach exhibits a relative lack offlexibility with regard to programming new animation behaviors in agraphical user interface. The key-framing script comprises a compiled,non-editable, sequence of animation instructions that morph a displayelement (or composition of elements) between a designated beginning andend point. The known key-framing animation approach of selecting twopoints in an animation sequence and then executing the program scriptbetween those two points aids programmers seeking to implement animationbehavior embodied within the previously created/compiled animationscripts. However, the key-framing approach limits the scope of supportedanimations to the linear progressions defined by an existing baseanimation script. The base animation script development is hindered bythe need to identify and code all the supported animation behaviorsbefore shipping the animation scripts to users/developers. During thelifetime of the animation script, many instances are likely to arisewhere a desired animation behavior is not contained in the script.However, the script is not editable by users/developers and thereforecannot be used to execute new desired animation behavior that was notpreviously encoded in the compiled animation script.

[0008] There is therefore a need for a more efficient, flexible, andless costly way of implementing interesting, informative, and meaningfulanimation behaviors into graphical user interface displays.

SUMMARY OF THE INVENTION

[0009] An animation system described, by way of example, and claimedherein below, provides a framework for defining, creating, and executinganimation behavior for both graphical user interface display elementsand non-visual parameter values. The animation behavior, when applied toan element, causes the value associated with the property to vary overtime when the animation behavior is active.

[0010] The animation system is incorporated into a system that utilizesa display structure for maintaining a set of elements that correspond toobjects displayed within a scene such as a display window of a computersystem graphical user interface. The elements include a variableproperty value affecting a display characteristic of the element.Examples of such a variable property is a position, a dimension, acolor, opacity, etc.

[0011] The animation system also utilizes a property system. Theproperty system maintains properties associated with the elementsmaintained by the display structure. The property system supportsdynamic properties—ones that are capable of being modified over time.

[0012] The animation system also includes animation classes that specifyparticular animation behaviors executable upon a base value. Animationobjects are instantiated from the animation classes. Such animationobject instances provide time varying values affecting values assignedto the dynamic properties. Such animation objects are created andattached to properties maintained by the property system under thedirection of an application that is driving a display including theelements that vary over the course of time in accordance with associatedanimation objects.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] While the appended claims set forth the features of the presentinvention with particularity, the invention and its advantages are bestunderstood from the following detailed description taken in conjunctionwith the accompanying drawings, of which:

[0014]FIG. 1 is a block diagram depicting an exemplary computer systemfor carrying out an embodiment of the invention;

[0015]FIG. 2 is an exemplary high level schematic diagram depicting theprimary components of a graphics management architecture including ananimation system for supporting animation of graphical display elements;

[0016]FIG. 3 is a flowchart summarizing an exemplary sequence ofrepeated steps performed in a system embodying the present invention tomaintain/render an animated graphical user interface;

[0017]FIG. 4 is an exemplary animation class definition for carrying outanimation on a specified element property;

[0018]FIG. 5 summarizes a set of exemplary animation constructor typesfor animating an element property;

[0019]FIG. 6 summarizes an exemplary animation collection class for ananimation architecture embodying the present invention; and

[0020]FIG. 7 summarizes an exemplary dynamic animation collection classfor an animation architecture embodying the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0021] A graphical user interface architecture is described thatincludes an animation system, a property system, and a display elementorganization structure. These components, in combination, supportproperty-based animation of graphical user interface displayelements—and even non-display values. The disclosed animationarchitecture includes an animation system including animation classes,interfaces and collections that facilitate creating and trackinganimation instances that are attached to a variety of graphical display(and non-display) elements (e.g., icons, dialog boxes, scroll bars,etc.) to achieve desired animation behavior by the elements. Animatingthe display elements is achieved by changing property values of thedisplay elements. In an embodiment of the invention, changes to aproperty value are driven by an animation object instantiated from ananimation class and attached to the property.

[0022] In an embodiment of the invention, graphical animation isachieved by associating an animation collection with a renderingoperation on a particular element within an element free. Once ananimated element is initially drawn, the rendering system updates theelement's display state at intervals in accordance with an animationbehavior defined by components of animation objects instantiated fromspecified animation classes.

[0023] In an embodiment of the invention, animation is designated atmultiple levels in a graphical display system having differing refreshcycles. Certain, easily calculated, animations are updated at arelatively high refresh rate. Other, more complicated animations, suchas those affecting other graphical display objects, are updated at arelatively low refresh rate.

[0024] When taken as a whole, the animation architecture describedherein provides a highly flexible platform for executing a variety ofnew animation behaviors and attach the new behaviors to display elementsto create new and highly engaging animated display interfaces.

[0025]FIG. 1 illustratively depicts an example of a suitable operatingenvironment 100 for carrying out the animation architecture embodyingthe present invention. The operating environment 100 is only one exampleof a suitable operating environment and is not intended to suggest anylimitation as to the scope of use or functionality of the invention.Other well known computing systems, environments, and/or configurationsthat may be suitable for use with the invention include, but are notlimited to, personal computers, server computers, laptop/portablecomputing devices, hand-held computing devices, multiprocessor systems,microprocessor-based systems, network PCs, minicomputers, mainframecomputers, distributed computing environments that include any of theabove systems or devices, and the like.

[0026] The invention is described in the general context of a set ofsteps and processes carried out by computer-executable instructions,such as program modules, being executed by a computer. Generally,program modules include routines, programs, objects, components, datastructures, etc. that perform particular tasks or implement particularabstract data types. Though the exemplary embodiment is described withreference to locally executed processes on a single computer system, theinvention is potentially incorporated within network nodes operating indistributed computing environments where tasks are performed by remoteprocessing devices that are linked through a communications network. Ina distributed computing environment, program modules are generallylocated in both local and remote computer storage media including memorystorage devices.

[0027] With continued reference to FIG. 1, an exemplary system forimplementing the invention includes a general purpose computing devicein the form of a computer 110. Components of computer 110 may include,but are not limited to, a processing unit 120, a system memory 130, anda system bus 121 that couples various system components including thesystem memory to the processing unit 120. The system bus 121 may be anyof several types of bus structures including a memory bus or memorycontroller, a peripheral bus, and a local bus using any of a variety ofbus architectures. By way of example, and not limitation, sucharchitectures include Industry Standard Architecture (ISA) bus, MicroChannel Architecture (MCA) bus, Enhanced ISA (EISA) bus, VideoElectronics Standards Association (VESA) local bus, and PeripheralComponent Interconnect (PCI) bus also known as Mezzanine bus.

[0028] Computer 110 typically includes a variety of computer readablemedia. Computer readable media can be any available media that can beaccessed by computer 110 and includes both volatile and nonvolatilemedia, removable and non-removable media. By way of example, and notlimitation, computer readable media may comprise computer storage mediaand communication media. Computer storage media includes both volatileand nonvolatile, removable and non-removable media implemented in anymethod or technology for storage of information such as computerreadable instructions, data structures, program modules or other data.Computer storage media includes, but is not limited to, RAM, ROM,EEPROM, flash memory or other memory technology, CD-ROM, digitalversatile disks (DVD) or other optical disk storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or any other medium which can be used to store the desired informationand which can accessed by computer 110. Communication media typicallyembodies computer readable instructions, data structures, programmodules or other data in a modulated data signal such as a carrier waveor other transport mechanism and includes any information deliverymedia. The term “modulated data signal” means a signal that has one ormore of its characteristics set or changed in such a manner as to encodeinformation in the signal. By way of example, and not limitation,communication media includes wired media such as a wired network ordirect-wired connection, and wireless media such as acoustic, RF,infrared and other wireless media. Combinations of the any of the aboveshould also be included within the scope of computer readable media.

[0029] The system memory 130 includes computer storage media in the formof volatile and/or nonvolatile memory such as read only memory (ROM) 131and random access memory (RAM) 132. A basic input/output system 133(BIOS), containing the basic routines that help to transfer informationbetween elements within computer 110, such as during start-up, issometimes stored in ROM 131. RAM 132 typically contains data and/orprogram modules that are immediately accessible to and/or presentlybeing operated on by processing unit 120. By way of example, and notlimitation, FIG. 1 illustrates operating system 134, applicationprograms 135, other program modules 136, and program data 137.

[0030] The computer 110 may also include other removable/non-removable,volatile/nonvolatile computer storage media. By way of example only,FIG. 1 illustrates a hard disk drive 140 that reads from or writes tonon-removable, nonvolatile magnetic media, a magnetic disk drive 151that reads from or writes to a removable, nonvolatile magnetic disk 152,and an optical disk drive 155 that reads from or writes to a removable,nonvolatile optical disk 156 such as a CD ROM or other optical media.Other removable/non-removable, volatile/nonvolatile computer storagemedia that can be used in the exemplary operating environment include,but are not limited to, magnetic tape cassettes, flash memory cards,digital versatile disks, digital video tape, solid state RAM, solidstate ROM, and the like. The hard disk drive 141 is typically connectedto the system bus 121 through an non-removable memory interface such asinterface 140, and magnetic disk drive 151 and optical disk drive 155are typically connected to the system bus 121 by a removable memoryinterface, such as interface 150.

[0031] The drives and their associated computer storage media discussedabove and illustrated in FIG. 1, provide storage of computer readableinstructions, data structures, program modules and other data for thecomputer 110. In FIG. 1, for example, hard disk drive 141 is illustratedas storing operating system 144, application programs 145, other programmodules 146, and program data 147. Note that these components can eitherbe the same as or different from operating system 134, applicationprograms 135, other program modules 136, and program data 137. Operatingsystem 144, application programs 145, other program modules 146, andprogram data 147 are given different numbers here to illustrate that, ata minimum, they are different copies. A user may enter commands andinformation into the computer 100 through input devices such as akeyboard 162 and pointing device 161, commonly referred to as a mouse,trackball or touch pad. Other input devices (not shown) may include amicrophone, joystick, game pad, satellite dish, scanner, or the like.These and other input devices are often connected to the processing unit120 through a user input interface 160 that is coupled to the systembus, but may be connected by other interface and bus structures, such asa parallel port, game port or a universal serial bus (USB). A monitor191 or other type of display device may also be connected to the systembus 121 via an interface, such as a video interface 190. In addition tothe monitor, computers may also include other peripheral output devicessuch as speakers 197 and printer 196, which may be connected through anoutput peripheral interface 195.

[0032] The computer 110 potentially operates in a networked environmentusing logical connections to one or more remote computers, such as aremote computer 180. The remote computer 180 may be a personal computer,a server, a router, a network PC, a peer device or other common networknode, and typically includes many or all of the elements described aboverelative to the computer 110, although only a memory storage device 181has been illustrated in FIG. 1. The logical connections depicted in FIG.1 include a local area network (LAN) 171 and a wide area network (WAN)173, but may also include other networks. Such networking environmentsare commonplace in offices, enterprise-wide computer networks, intranetsand the Internet.

[0033] When used in a LAN networking environment, the computer 110 isconnected to the LAN 171 through a network interface or adapter 170.When used in a WAN networking environment, the computer 110 typicallyincludes a modem 172 or other means for establishing communications overthe WAN 173, such as the Internet. The modem 172, which may be internalor external, may be connected to the system bus 121 via the user inputinterface 160, or other appropriate mechanism. In a networkedenvironment, program modules depicted relative to the computer 110, orportions thereof, may be stored in the remote memory storage device. Byway of example, and not limitation, FIG. 1 illustrates remoteapplication programs 185 as residing on memory storage device 181. Itwill be appreciated that the network connections shown are exemplary andother means of establishing a communications link between the computersmay be used.

[0034]FIG. 2 is a high level schematic diagram identifying components ofa graphical display architecture embodying the present invention andincorporating a set of interacting functional components of an animationsystem. The graphical display architecture depicted in FIG. 2 is dividedinto a set of functional components to aid the description of anexemplary embodiment of the present invention. The present invention isnot limited to the arrangement of the components in the illustrativelydepicted manner. Rather, the functionality of the components describedherein below is grouped differently in alternative embodiments of theinvention.

[0035] The animation system includes a number of subcomponents that, incombination, facilitate animating graphical display objects (as well asnon-visual parameters) based upon high level instructions submitted byan application 200. The application 200 can be any application orcontrol residing either inside or outside the operating system. Theanimation infrastructure described herein enables delegating, to asubstantial extent, programming and executing animation to generalizedanimation components. In an embodiment of the invention, rather thancalculating updated bitmaps, the application 200 submits commands to theanimation system specifying/defining animation for one or more displayobjects.

[0036] In accordance with the application 200's commands, the animationsystem builds animation objects. Animation objects, once instantiated,can be associated with an element tree 202. The element tree 202 iscreated in response to events generated by the application 200. Examplesof such events include the start of the application 200, or some otherexecuted command resulting in the creation of a new view. Thereafter,the application creates new elements, and later removes the elements, inthe element tree 202.

[0037] The element tree 202 comprises a hierarchically arranged set ofelements. In an embodiment of the invention, the element tree 202structurally defines a document. Each element describes an object that,in most cases, corresponds to a visual image displayable, for example,on a graphical user interface. Examples of elements include: buttons,tables, table cells, list controls, frames, images, and paragraphs (flowpanels). Elements in the element tree 202 generally include one or moreproperties (e.g., color, height, width, position, transparency, etc.).Values assigned to the properties of an element contribute to defining adisplay state of the element. In an embodiment of the invention,animation objects are assigned to one or more element/propertycombinations. Thereafter, the animation object instances execute torender an animation behavior on an element's property according to atimeline with which each of the animation object instances isassociated.

[0038] “Timelines”

[0039] Timing and timelines drive the animation system described herein.The timing aspect of the animation system described herein is aderivative of the Synchronized Multimedia Integration Language (SMIL2.0) W3C specification. Each animation object, once created and beforeexecution, is associated with a timeline (e.g., a time sequencedefinition) that controls the progression of a sequence of changesassociated with the animation object's defined behavior. Furthermore,the above-mentioned timeline only defines a local/relative timingsequence of an animation behavior (e.g., duration of the animation,repeats, accelerations, etc.). An animation object is thus incapable ofexecuting until the animation object has been assigned a “parent”timeline (either directly or indirectly through another object).Therefore, in order to execute the animation object, the relativetimeline is attached to a “parent” timing definition (“parent timeline”)that ties the relative timing definition of the animation object to anactual execution time defined by a parent timeline. Thus, the parenttimeline does not govern the animation behavior of an animation object.Instead, the parent timeline governs the external behavior such as, forexample, when the animation actually commences. The timelines aremaintained in a hierarchical timing tree structure, and individualtimelines have attributes that define their behavior relative to aparent timeline. A top level timeline is defined relative to a root(e.g. document, page, frame, etc.) timeline.

[0040] There are a number of ways to associate a parent timeline with ananimation object that has its own internal timeline defining its localanimation timing behavior. By way of example, a parent timeline is atiming definition to which the animation object is attached. In oneexemplary mode of designating a timeline, an entity (e.g., anapplication) requesting creation of an animation object specifies aparent timeline to which the timeline for the animation object isattached. In this case, the timeline of the animation object identifiesthe parent timeline at the time of creation, and the created animationobject is the actual executed animation object (as opposed to a copy)used by one or more element/property combinations with which theanimation object is thereafter associated.

[0041] In another exemplary mode of designating a timeline for ananimation object, a partially complete animation object class is createdthat includes its own timeline, but does not include a parent timeline.This incomplete form of animation object definition (lacking a parenttimeline) is referred to herein as an “animation template.” Theanimation templates are not executed, instead copies (or clones) ofanimation templates are created, and the new animation instances areeach assigned an animation parent timeline of an element to which thenew animation is attached. In such instances, the parent timeline of acloned animation object is the parent timeline specified by an elementto which the cloned animation object is attached. The absence of aspecific parent timeline timing definition enables creating multipleclones from a single animation template, and each “cloned” animationobject adopts element-specified animation execution (e.g., start, pause,etc.) timing defined by the element to which it is attached. Because thepresent system supports later designation of a parent timeline,animation objects created for placement onto the element tree 202 do notrequire explicit designation of a parent timeline at the time ofcreation. Though such timing information is completed to enable theanimation to be executed.

[0042] Alternatively, the Application 200 passes animation objectsdirectly to a media integration layer (MIL) 204 via a media integrationlayer (MIL) interface 206. The MIL 204 is described, by way of example,in Beda et al., U.S. patent application Ser. No. 10/184,795, filed onJun. 27, 2002, entitled “Multiple-Level Graphics Processing System andMethod,” the contents of which are expressly incorporated herein byreference, including the contents of any references contained therein.In an embodiment of the invention, animation objects passed directlyfrom the application 200 into the MIL interface 206 require explicitdesignation of a parent timeline, or the animation object is notexecuted.

[0043] The MIL 204 includes a set of graphical display object renderingand control components accessed via the MIL interface 206. The MILinterface 206 is described, by way of example, in Beda et al., U.S.patent application Ser. No. 10/184,796, filed on Jun. 27, 2002, entitled“Generic Parameterization for a Scene Graph,” the contents of which areexpressly incorporated herein by reference, including the contents ofany references contained therein. The MIL interface 206 is an interfacethat the application 200 or a presenter system 208 (described below)rely upon to build up a low-level description of a display frame of anapplication. The MIL interface 206 includes a set of method calls, suchas: DrawLine( . . . ), PushTransform( . . . ), and PopTransform( . . .). The calls serviced by the MIL interface 206 describe ascene/document/or graphical user interface.

[0044] The invention addressed herein provides an infrastructure fordefining animation for graphical objects as well as any parameter valuesthat change over time. Thus, the actual animation can be executed by anyof a variety of graphics rendering engines, including by way of example,the MIL 204 summarized herein.

[0045] The elements maintained by the element tree 202 represent highlevel graphical items (e.g., buttons, scroll bars, etc). In anembodiment of the invention, such graphical objects are described athigh level that is not directly usable by the MIL 204 components. Thus,a presenter within a presenter system 208 compiles/translatesconstituents of the element tree 202, with which the presenter isassociated, into visuals (e.g., lines, filled rectangles, etc.) thatmake up the elements of the element tree 202. The presenter system 208passes the visuals into the MIL 204 via the MIL interface 206. There aremany ways to carry out the functionality of the presenter system 208. Anexemplary embodiment of the presenter system 208 is described in detailin Parikh et al., U.S. patent application Ser. No. ______(serial numbernot yet assigned), filed on May 9, 2003 (Express Mail EV 329734584 US),and entitled “SYSTEM FOR HOSTING GRAPHICAL LAYOUT/PRESENTATION OBJECTS,”the contents of which are expressly incorporated herein by reference,including the contents of any references contained therein.

[0046] In a particular embodiment of the invention, the MIL 204 includesa high-level visual tree 210 that is capable of processing the visualspassed by the presenter system 208 into the MIL 204 via the MILinterface 206. The high level visual tree 210 contains a structured setof primitives (e.g., lines, rectangles, images, etc.). The structuredset of primitives that describe a single image frame for an application.The high level visual tree 210 supports a class of animations referredto as “independent animations.” The independent animations, describedfurther herein below, do not rely upon the presenter system 208 layoutfunction to achieve animation.

[0047] A low level visual tree 212 is a potentially flattened version ofthe high level visual tree 210. The low level visual tree 212 isconfigured to rapidly render and execute independent animations passedto the low level visual tree 212 via the high level visual tree 210. Thelow level visual tree 212 potentially executes multiple frames betweenupdates to its structure from, for example, the high level visual tree210.

[0048] The low level visual tree 212 is configured to interface tooutput drivers. A remote machine network communication driver 214 is anobject corresponding to a machine at which the application 200 rendersoutput. The machine is potentially a different machine from a machineupon which the application 200 executes. In such case, the application200 communicates its visual output over a network connection to displayoutput on a remote machine for a user of the application 200.

[0049] Alternatively, the low level visual tree 212 renders output to agraphical display driver 216. The graphical display driver 216represents the communication of the frame display data to hardware on alocal machine that is responsible for drawing the frame to an outputdisplay device (e.g., a visual display screen) for a machine currentlyrunning the application 200 for a local user.

[0050] When objects are being animated, a render queue item 213 ensuresthat the animations stay in sync with one other. The render queue item213 is created each time a new frame needs to be rendered—e.g., whenchanges are made to the element tree 202 or when animation objects causevalues to change. The render queue item 213 dies as soon as it iscompletely processed. The render queue item 213, in carrying out itssynchronization role, organizes the following processes: ticking atiming tree 228 (described below) and therefore invalidating dependentlyanimated properties; invoking the presenter system 208 to finalize alayout and update the high level visual tree 210 after the tickingprocedure is complete; and after the presenter system 208 finalizes thelayout, requesting the visual tree 210 to compile and propagate thechanges down to the low level visual tree 212. The steps in carrying outthe functions of the render queue item 213 are described herein belowwith reference to FIG. 3.

[0051] Having described certain exemplary function blocks that maintainand generate a frame of data according to provided animated values,attention is now directed to the sources of animated properties withinthe element tree 202 and their time-driven changes. A property system220 is responsible for maintaining values for properties. The propertysystem 220 stores and calculates values on elements so that they can beused by the presenter system 208 to create the high level visual tree210. The property system 220 supports an inheritance model for propertyvalues wherein an element's value for a particular property is inheritedby a set of children of the element.

[0052] As illustratively depicted in FIG. 2, the property system 220receives input values from many sources. The application 200 sets basevalues for dynamic properties (and also retrieves their current values)maintained by the property system 220. The element tree 202 requestsvalues, for properties of elements within the element tree 202, from theproperty system 220 to give to the presenter system 208. The presentersystem 208, in turn, uses the property values to generate input to thefor calls to the MIL interface 206. During the course of processing theelements of the element tree 202, the presenter system 208 requestsdynamic property base values and other information associated with theelements from the property system 220 to organize and assign values tothe elements making up a particular view with which the presenter system208 is associated.

[0053] The property system 220 prioritizes values from the differentsources. For instance, the property system 220 enables a property valuespecified locally to take higher precedence over a value specified in aproperty sheet or a value inherited from a parent. The property system220 includes logic to sort values provided by various sources and returnthe highest priority value to any recipient of the value. The propertysystem 220 takes into consideration any active animations attached to aproperty when calculating the current value for the property. If a userrequests a value from a particular source, then the property system 220handles such request.

[0054] Animation objects, that make changes to property valuesmaintained by the property system 220, are instantiated from animationclasses 222 that define and execute ways to modify a property valuebased upon a timeline associated with the animation object instances (ora parent thereof). An animation class object instance is created by theapplication 200. The application 200 also sets values on the animationobjects instantiated from the animation classes 222. The application 200is also capable of requesting a current value on a particular animationclass object. An animation class object is removed when no referencesexist for the animation class object. The animation classes 222 eachhave specifiable properties such as From, To, and Duration, thatdescribe a particular animation behavior.

[0055] Animation classes are typed so that different classes exist fordifferent animation behaviors and their corresponding data types.Examples of animation classes include:

[0056] FloatAnimation—providing a floating point value,

[0057] BoxUnitAnimation—providing dimensions for a presenter box,

[0058] PointAnimation—providing the top, left position of a rectangle,

[0059] ColorAnimation—providing a time-changing color value; and

[0060] BoolAnimation—providing a Boolean value.

[0061] Instances of the animation classes 220 are immutable. Thus, oncethey are created, their property values can never be changed. This meansan application writer can re-use an animation instance in multipleplaces without concern that its defined behavior will be changed.

[0062] Animation collection classes 224 organize animation classes 222.An animation collection class is created by the application 200. Theapplication 200 specifies one or more animation classes 222 containedwithin an animation collection class. The application 200 then sets ananimation collection class as the collection of animations that willanimate a dynamic property in the property system 220. The application200 can also associate an animation collection class instance with anydynamic property associated with any particular element in the elementtree 202. The application 200 is able to enumerate the containedanimation classes in a particular animation collection class of theanimation collection classes 224, as well as request a composedanimations value from the animation collection class. An animationcollection class instance is garbage collected when no references existfor the particular animation collection class instance.

[0063] An animation collection is a collection of animation objects thatprocess a same data type. An animation collection class is aware of therelative priority of the animation classes in its list and how tocompose the animation classes together according to a base value passedinto the animation collection class instance, and the animation classreturns a current value. In an embodiment of the invention, animationclasses are chained together in animation collection classes. The inputof the animation collection receives a base property value. The firststage (animation object) renders a modified property value of the sametype as the input to a next potential stage (in the case of multipleanimation objects within an animation collection class object). Thepipelined processing of the base value by the pipelined animationobjects of the animation collection renders a current value for theanimated property. The result of such pipelining is the creation of aserially executed composite animation function.

[0064] An animation collection class exists for each type of propertyvalue for which animation is supported (e.g., FloatAnimationCollection,BoxUnitAnimationCollection, PointAnimationCollection,ColorAnimationCollection, and BoolAnimationCollection). This list ofanimation collection class types is merely exemplary. Those skilled inthe art will readily appreciate the potential wide breadth of differentanimation collection class types. As with animation classes 220,instances of an animation collection class from the animation collectionclasses 224 are immutable.

[0065] A dynamic animation collection class 226 builds upon thefunctionality of, the animation collection classes 224. An instance ofthe dynamic animation collection class 226 holds onto a reference to ananimation collection class instance of the animation collection classes224. In addition, a dynamic animation collection object instance holdsonto a reference to an element within the element tree 202 and to aproperty on the element that the dynamic animation collection instanceis animating. An application writer, in an embodiment of the invention,cannot create or access a dynamic animation collection instance.Instead, the property system 220 creates a dynamic animation collectioninstance upon receiving a request from the application 220.

[0066] A dynamic animation collection object instance is created by theproperty system 220 when an animation collection class instance isassociated with a dynamic property. The dynamic property holds and/orcalculates a value associated with a single defining property for anelement in the element tree 202, such as width, height, top, left, orany other defining property of any kind of element. The dynamicanimation collection also holds an animation collection instantiatedfrom an animation class of the animation collection classes 224 and thusassociates the animation collection class with a particularelement/property combination in the element tree 202. If the propertysystem 220 is asked for a current value of a dynamic property, theproperty system 220 determines whether the dynamic property has anassociated dynamic animation collection object instantiated from thedynamic animation collection class 226, and the property system 220processes the base value through any currently-active animation classesin the dynamic animation collection to provide a current animated value.In an embodiment of the invention, when the property system 220 requestsa particular dynamic animation collection object for a current value,the specified dynamic animation collection passes the request onto anappropriate animation collection object instantiated from one of theanimation collection classes 224. The animation collection object, inturn, loops through its set of animation objects instantiated from theanimation classes 222 to render their current values to provide thebasis for rendering a final value by the animation collection object toits calling dynamic animation collection.

[0067] Some animations created by the application 200 may not specify aparent timeline and expect the animation system to choose theappropriate parent timeline for a requested animation. During theassociation process, the property system 220 initially determineswhether each animation class within the animation collection class has aparent timeline. If any animation class is not associated with a parenttimeline, then a new animation class is created that is associated witha parent timeline of a display element with which the dynamic animationcollection is associated. Furthermore, it is noted that if the parenttimeline associated with a display element is changed, then the dynamicanimation collection is rebuilt to reflect the change in the parenttimeline.

[0068] To properly function, all animation classes within an animationcollection class must eventually specify a parent timeline that governsthe timing of their execution. If all of the animation classes in thespecified animation collection class are associated with parenttimelines, then the dynamic animation collection uses the specifiedanimation collection class. Otherwise, in view of the immutability ofanimation classes and animation collection classes, the property system220 creates a new animation collection class, and the new animationcollection class includes new animation classes, each having an assignedparent timeline. Once the property system 220 has created the newanimation collection class with each animation object having a parenttimeline, the property system 220 gives the animation collection classto the dynamic animation collection associated with the element/dynamicproperty pair. If there is not yet a dynamic animation collectionassociated with this pair, the property system will create a new one226.

[0069] As noted many times above, timing drives the animation behaviorsassociated with the animation objects attached to properties of elementsin the element tree 202. As used herein, a timeline is an instance of atiming entity that maintains a runtime state according to a set oftiming attributes. The timing tree 228, in an embodiment of theinvention, is a data structure containing timing nodes (timelines)arranged in a hierarchical manner. The relationship between timing nodesis defined by inheritance rules and by the node-specific timingattributes of each timeline corresponding to a timing node in the timingtree 228. The inheritance rules include defining offsets of childrenbegin times relevant to parent begin time. Furthermore, the inheritancerelationships specify control relationships. For example, if a parent isrestarted, repeated, paused, resumed, seeked or ends, so to do all thechildren (and their children, etc.). Such relationships enable startinga whole group of child timelines through an action on a single parenttimeline. The timing tree 228 holds onto: (1) timelines that potentiallydrive changes to values of animation class instances, and (2) containertimelines which contain other timelines. Progress values derived fromthe timelines are used to calculate any given animation object's currentvalue. The timing tree 228 is created at startup time of the application200.

[0070] The timing tree 228 carries out a timing event notification rolefor the animation infrastructure depicted in FIG. 2. Initially, when adynamic animation collection is instantiated, a request is issued by thedynamic animation collection to the timing tree 228 to issue anotification whenever an animation instance in its animation collectionclass object has progressed. When the dynamic animation collectionreceives a notification from the timing tree 228 that one of it'sanimations has progressed, the dynamic animation collection instancenotifies the property system 220 that the dynamic property on thedisplay element, with which it is associated, is now invalid. Theinvalidation of a display element property in-turn begins a processreferred to herein as dependent animation. During dependent animationprocessing, the presenter system 208 is requested to build the highlevel visual tree 210 in accordance with the value change associatedwith the animation.

[0071] The timing tree 228 also performs a progress measurement andreporting role for instances of the animation classes 222. In responseto invalidation, instances of the animation classes 222 are requested toreport their current values. The animation classes 222 query the timingtree 228 for a timeline progress value with which each is associated.The animation classes 222 thereafter calculate their current valuesbased upon a progress value supplied by the timing tree, and provide thecurrent values to any requesting entity.

[0072] The render queue item 213 also interacts with the timing tree228. The render queue item is a queue item in the operating system queuewhich, when executed, causes the application/page/scene generated by theapplication 200 to be compiled down to the low level visual tree 212 andeventually be rendered onto the display device. The first thing therender queue item performs, once invoked, is “tick” the timing tree 228.This has the effect of having the timing tree update its timelines tothe current time. As a result, the timing tree 228 sends outnotifications which may cause many invalidations in the property system220. Progress values of independent animations are updated as well whenthe tick is executed. If, during the processing of the render queue item213, the timing tree 228 is modified, the render queue item will loopand “re-tick” at the same time until the timing tree 228 stabilizes.

[0073] Independent/Dependent Animations

[0074] Both independent and dependent animations have been mentionedabove. In an embodiment of the invention, the animation system depictedin FIG. 2 supports at least these two types of animation instances—whoseclassification is based upon their relationships to other animationinstances. Independent animation instances do not impact the layout of aview and can therefore be refreshed at a higher rate. An example of anindependent animation is a color animation. The color of an object doesnot modify its width or height, and therefore the color-change animationdoes not affect how the color-change animated element is laid out (e.g.,size or position) on the page.

[0075] Dependent animations generally change a layout of an element withwhich the dependent animations are associated, and therefore dependentanimations require recalculation of a graphic user interface layout. Thedependent animation instances are stored within the element tree 202structure to ensure proper processing of all affected display elementproperties. Due to potentially significantly greater calculation andmemory access requirements, dependent animations are calculated at apotentially lower refresh rate by the MIL 204.

[0076] Three Levels/Stages for “Animation” Classes

[0077] In an embodiment of the present invention, the animation behaviorapplied to display element properties is implemented through threelevels of classes, and their corresponding instances. With continuedreference to FIG. 2, the animation classes 222 comprise a set of objectclasses defining objects capable of computing particular definedanimation operations on a property value (typically a single animationbehavior).

[0078] At the next level, the animation collection classes 224 define aset of objects that group/assign one or more individual animationclasses from the animation classes 222 into a single animation classdefinition—thereby supporting creation of composite animation behaviorson a single element property.

[0079] At the next level, the dynamic animation collection 226 definesan object type to carry out/execute an animation behavior, defined byone of the animation collection classes 224, on a property of an elementwithin the element tree 202. Such functionality is facilitated byinstances of the dynamic animation collection 226 holding onto: areference to an animation collection class instance of the animationcollection classes 224; and a reference to an element within the elementtree 202 and to a property on the element that the dynamic animationcollection instance is animating. A dynamic animation collection iscreated by the property system 220 when an animation collection classinstance is associated with a dynamic property. The dynamic propertyholds and/or calculates a value associated with a single definingproperty for an element in the element tree 202, such as width, height,top, left, or any other defining property of any kind of element. Thedynamic animation collection also holds a reference to an animationcollection class object instantiated from one of the animationcollection classes 224 and thus associates the animation collectionclass object with a particular element/property combination in theelement tree 202.

[0080] Turning to FIG. 3, a set of steps are summarized for an exemplaryrendering sequence performed by the render queue item 213 of FIG. 2. Asexplained above, the render queue item 213, when executed, causes theapplication/page/scene generated by the application 200 to be compileddown to the low level visual tree 212 for rendering by a display device.It is noted that this sequence of steps is exemplary, and the renderqueue item operation is modified in other embodiments of the invention.

[0081] Initially, during step 300, the render queue item 213 causes aticking of the timing tree 228. Ticking the timing tree 228 has theeffect of having the timing tree 228 update its timelines to the currenttime. As a result, the timing tree 228 sends out notifications which maycause many invalidations (e.g., invalidating dependently animatedproperties) in the property system 220. In an embodiment of theinvention, a Changed event is raised by animation objects that have beenaffected by the updated time. These events are collected and processedby an animation object's associated Dynamic Animation Collection objectinstance. The Dynamic Animation Collection object, in turn, invalidatesits dynamic property on an element. Progress values of independentanimations are updated as well when the tick is executed at step 300.

[0082] After ticking the timing tree 228, during step 310 a layoutprocess is performed by the render queue item 213. During the layoutprocess 310 the high level visual tree 210 is updated according to anychanges to the element tree 202 since the last execution of a renderqueue item. In an embodiment of the invention, presenters that areresponsible for laying out graphical elements in a view that havechanged property values (as a result of the ticking of the time), areinvalidated—meaning they must recalculate their layout and create a newhigh level visual tree incorporating the changes to the affected dynamicproperties. Also during step 310, the display system receives anddispatches requests from applications, the operating system shell, etc.that potentially affect the layout. Examples of such requests includehit tests, callbacks to user programs, and general application actionsaffecting the graphical display.

[0083] During the layout process 310, the timing tree 228 structure canpotentially change (e.g., a new timing node was added, an existing nodewas removed, a new reference was established to an existing timing node,etc.). If, at step 320 it is determined that the timing tree structurechanged, then control passes back to step 300 and the timing tick isre-executed on the timing tree 228 structure in its new form.

[0084] If the timing tree 228 has not changed in structure, then controlpasses from step 320 to a Render step 330 wherein the high level visualtree 210 compiles and propagates new/updated graphical display data tothe low level visual tree 212. The low level visual tree 212, based uponthe received changes, renders recalculated output to the drivers 262and/or 264.

[0085] Thereafter, during step 340, the timelines associated with thedynamic animation collection are queried to determine a next time thatit needs to be ticked (nearest event). If no further ticks are needed,then control passes to the End 360. If additional ticks of the tree areneeded, then control passes to step 350 wherein a new instance of therender queue item 213 is created for the animated element property'sdynamic animation collection instance. The new render queue itemspecifies a time at which it should be executed. If the specified timeof execution is some time that has not yet been reached, then the renderqueue item is initially placed in an inactive list. When the time isreached, the render queue item is placed within an active queue forexecution in accordance with the steps set forth in FIG. 3. Aftercreated the new render queue item, control then passes to the End 360.

[0086] Animation behavior for an element property, is carried out by oneor more animation objects instantiated from the animation classes 222.Each animation object includes an animation function that takes a firstset of inputs (including at least a current timeline value) and producesan output of a type suitable for rendering an animated display element.Various ones of the animation classes 222 (e.g., PointAnimation) converta timeline progress value into an appropriate data type (e.g., a point)for an element property.

[0087] Turning to FIG. 4, an exemplary high-level animation classstructure is summarized. The various animation classes follow a commonpattern and implement a similar set of interfaces. The differences ariseprimarily in the data types of properties, and in the calculationsperformed (in view of the particular data type such as: floating point,Boolean, point, etc.) to assign a current value to an input value inview of a calculated progress value. Such modifications are well withinthe skill of those skilled in the art in view of the examples anddescription of the functionality of animation classes contained herein.

[0088] In an embodiment of the invention, the animation class structureincludes a set of Animation Properties 400. A From property designates astarting animation value. A To property specifies an ending animationvalue. A By property specifies a change (delta) value at the end of ananimation. Rather than specifying an explicit end value in the Toproperty, the By property specifies a difference between an endinganimation value and an initial animation value.

[0089] An animation class can comprise multiple segments utilizingdifferent timing parameters within each segment. A KeyValues propertyspecifies a list of values for an animation. An interpolation methodproperty specifies a method for interpolating between two key valuesspecified in the KeyValues property. Examples of interpolation methodsinclude: discrete, linear, paces, and spline. A KeyTimes propertydesignates a list of time values used to control the pacing of theanimation. This list contains the same number of elements as theKeyValues list. The list is ordered in increasing time values, and thefirst value in this list is 0 and the last 1 (unless InterpolationMethodis set to Discrete, in which case the last value may be anything lessthan or equal to 1). A KeySplines property specifies a set of Beziercontrol points associated with a KeyTimes list. The Bezier controlpoints define a cubic function that controls the interval pacing of theanimation. This list contains one less element than the KeyTimes list.This list is only used if the InterpolationMethod attribute is set toSpline.

[0090] The animation properties within an animation class structureinclude certain Boolean attributes. An IsOverridingBaseValue property isset to True if the timeline of the animation object is active or in afill period. Furthermore, an IsAccumulating property enables a repeatedanimation sequence to have a cumulative effect upon an element'sproperty. When the IsAccumulating property is set to True, rather thanrepeating the same trajectory on every iteration of a repeated animationsequence, an animation accumulates the effect of each iteration, inessence composing with itself and building upon a previousanimation-induced change to an element's property.

[0091] A UsesBaseValue property returns True if the return value ofGetValue for the animation object (described below in association with aset of methods 420) depends on the base value (provided to the animationobject). If the UsesBaseValue property returns False, then the animationobject ignores the base value altogether. If the animation object is ina list, the UsesBaseValue property allows an optimization where only asubset of the animation objects need to be evaluated in some cases.

[0092] The animation class structure also includes a set of timingproperties 410. A CurrentTime property provides a current time local tothe timeline for the animation object. A ParentTimeline propertydesignates a timeline that is the timing parent of the animationobject's timeline. The ParentTimeLine property can reference any othertimeline, or one of two special reference values: Timeline.VisualParentor Timeline.RootTimeline. If the ParentTimeline property is set toTimeline.VisualParent then the timeline is auto-parented on use to thetimeline associated with the visual in which it is used. If the visualdoes not have an associated DefaultTimeline, then the parent visual isinspected, recursively. If the ParentTimeline property is set toTimeline.RootTimeline then this timeline is auto-parented on use to the“root” of the timing tree 228.

[0093] The set of timing properties also includes a Begin property fordesignating a time at which the timeline for the particular animationobject should begin. By default the begin time value is relative to aparent timeline's begin time, but a offset is also potentially specifiedproviding a time relative to some other timeline's begin or end time. Inthe latter case, the other timeline must be parented to the sametimeline as the timeline for this particular animation object. ADuration property on an animation object designates a duration of asingle period from beginning to end. A Progress property designates thecurrent progress value of the timeline. If IsOverridingBaseValue(described herein below) is false, then the Progress property returns 0.In all cases, the return value of the Progress property is always avalue between 0 and 1, inclusive.

[0094] In an embodiment of the invention, repeating an animation issupported. A RepeatCount property specifies a number of times a begin toend period should be repeated during the life of this animation-object.The RepeatCount property value is potentially a fractional value. Aspecial value, float.PositiveInfinity, indicates that the timelineshould repeat continuously. A CurrentRepeat property specifies a currentiteration of the timeline, if it repeats. The first iteration isiteration 1. If the IsOverridingBaseValue animation property is falsethe CurrentRepeat property returns 0.

[0095] A RepeatDuration property specifies a length of time for which abegin to end period should be repeated. This potentially results in afractional execution (repeat count). The RepeatDuration property valueof Time.Indefinite indicates that the timeline should repeat forever. Ifthe IsOverridingBaseValue property is false this property returnsTime.Unspecified. If values are specified for both the RepeatCountproperty and the RepeatDuration property, then the total active durationis the minimum of the two specified properties.

[0096] The timing properties for the animation classes also include anacceleration property that designates a value, between 0 and 1,representing a fraction of the simple duration spent in the timeacceleration phase. A deceleration property designates a value, between0 and 1, representing a fraction of the simple duration spent in thetime deceleration phase. Since the animation cannot simultaneouslyaccelerate and decelerate, the sum of the acceleration and decelerationproperty values does not exceed 1 (the simple duration).

[0097] An Autoreverse property designates whether the animation is toprogress from beginning to end and then back. If the Autoreverseproperty has a value of “True”, then the timeline progresses frombeginning to end and then immediately progresses backwards from end tobeginning. The timeline will be active for twice the amount of timespecified by the Duration property of the animation object.

[0098] An End property maintains a value specifying a maximum end timefor the timeline for the animation object. If the End property value isless than the sum of the Begin and Duration property values, then theactivation period is cut short by the End property value. In addition,all specified animation beginnings (scheduled or interactive) past thetime specified by the End attribute are ignored.

[0099] An EndSync property value defines an implicit duration of atimeline. The implicit duration specified by the EndSync property isused if the Duration property is not set explicitly. The implicitduration of a timeline can be defined by the timed object that itcontrols or by other timelines that may be parented to it.

[0100] A Fill property specifies a behavior of the timeline of theanimation object after the end time passes. By default, the timeline isonly “on” from begin to end, but if the Fill property is set to“Freeze”, then the timeline remains on past the end time. In that case,the progress value for the animation object after the end time is equalto whatever it was at the end time. Settings for the Fill property valueare Remove (the global default), Freeze, and Hold. A FillDefaultproperty designates a default value for the Fill property. If the Fillproperty value is not specified, then the value of the DefaultFillproperty specifies the fill behavior. In addition, this default isinherited by timelines parented to this one, unless they have their ownFillDefault attribute set. The possible values for the DefaultFillproperty are the same as for the Fill attribute.

[0101] A Restart property designates a behavior of the animationobject's timeline when a second (or later) begin time is reached. Bydefault, a begin time interrupts any active period and goes back to timet=0 for the timeline. However, if the Restart property is set toWhenNotActive, then a begin time that would interrupt an active periodis ignored. The possible values for the Restart property are: Always,WhenNotActive and Never. A Restart Default property designates a defaultvalue for the Restart property.

[0102] A Speed property designates a relative speed at which time shouldpass for the timeline for the animation object (compared to its parenttimeline). E.g., A value of 1 means normal speed, whereas a value of 2means that time elapses twice as fast (and, therefore, the perceivedduration ends up being only half that specified by the Durationattribute). This value may be negative, in which case time flowsbackwards in this timeline, from end to begin times, as if the parenttimeline was reversed.

[0103] A set of Boolean properties are included to identify the state ofthe animation object's animation. An IsForwardProgressing propertyidentifies whether progress in this timeline moves from 0 to 1 inrelation to wall-clock time. The IsForwardProgressing property takesinto account the effect of being nested in potentially reversedtimelines. If IsOverridingBaseValue is false, then IsForwardProgressingreturns the same value as that which this timeline's parent timelinewould return. An IsReversed property identifies whether the timeline isin a reversed period, as seen from the timeline's own local frame ofreference. This property, in contrast to the IsForwardProgressingproperty, does not take into account the effect of being nested inpotentially reversed timelines. If the IsOverridingBaseValue propertyvalue is false, then the Is Reversed property returns false.

[0104] Other properties relate to the state of the animation's state ofactivity. An IsChanging property identifies whether the timeline of theanimation object is active. In contrast, an IsPaused property returnstrue if the timeline is active, but the animation is paused.

[0105] The animation class also includes a set of methods 420. A set ofconstructor methods, within a particular animation class, createanimation objects incorporating particular animation behaviors of aspecific animation class type (e.g., float, Boolean, point, etc.). A setof animation constructor method types, corresponding to particularanimation behaviors, are identified, by way of example, in FIG. 5described herein below.

[0106] A BeginIn method receives as input an offset time value. TheBeginIn method triggers an interactive begin at a point in time in thefuture or past corresponding to the offset value. The input offsetparameter specifies a time in reference to the animation object's parenttimeline. If the parent timeline is not active, this method has noeffect.

[0107] Similarly, an EndIn method receives as input another relativetime value. The EndIn method triggers an interactive end at thespecified point in time in the future or past. The parameter is in theframe of reference of the animation object's parent timeline. If theparent timeline is not active, this method has no effect.

[0108] Methods are provided to stop/start the progression of theanimation object while it is active. A pause method pauses the animationobject's timeline and children that reference the animation object'stimeline. If this timeline is not active this method has no effect.Conversely, a resume method restarts the animation object's timeline andall of its children timelines. If this timeline is not active and pausedthis method has no effect.

[0109] A seek method enables moving directly to a particular point in ananimation execution sequence based upon a specified offset value. Theseek method changes the current time for this timeline—that potentiallyaffects all of its children timelines. If the timeline is not activethis method has no effect.

[0110] A GetUniqueInstance method receives a timeline as input, andreturns an instance of an animation object that can maintain its ownrun-time state separately from other instances. If the animation objectcontains auto-parented timelines, the returned instance has thosetimelines parented to the timeline passed in as a parameter.

[0111] A GetValue method takes as an input a base value, of a certaintype, and returns another value of the same type as the input basevalue. The value of the output depends both on the input (base value)and on the internal state of the modifier (e.g., animationobject/collection) to which it is passed. In particular, this means thatcalling GetValue more than once with the same input is not guaranteed toreturn the same output, and in fact it is expected to change during thecourse of an animation sequence. In the case of the animation objectclasses 222, the GetValue method receives a passed base value andreturns a value based upon its internal modifier definition computationof a progress value.

[0112] Finally, the animation class structure supports a set of events.A Changed event 430 is raised whenever the animation object's internalstate changes. The Changed event 430 flag is used to indicate thatre-rendering is needed (something has changed in position or dimension).A Begun event signal is raised when an object enters a period in whichits internal state is continually changing. An Ended event signal israised whenever the object leaves a period when its internal state iscontinually changing. A Repeated event is raised whenever the animationobject's timeline repeats its simple duration. A Reversed event israised whenever the direction of time changes on the animation object'stimeline. The events Paused, Resumed, and Seeked are raised in responseto completing a corresponding Pause, Resume and Seek method on theanimation object's timeline.

[0113] Turning to FIG. 5, a set of animation object behaviors areidentified. Each of the identified behaviors corresponds to a particularconstructor class supported, where appropriate, by each of the animationclass types listed previous herein above. A From constructor type 500creates an animation object that takes as its initial value a passed“From” value and progresses to a base value specified on the associatedproperty. A To constructor type 510 creates an animation object thattakes as its initial value the base value specified on the associatedproperty and progressed to a passed “To” value. A From-To constructortype 520 receives passed parameters designating the From and To propertyvalues for the animation object—the base value on the animated element'sproperty is not used during the animation. However, when the animationsequence ends the element property reverts to the base value unless theFill timing property on the animation object is “Freeze.”

[0114] Rather than specifying endpoints for an animation, an animationvalue range can be specified through an end point and an amount ofchange (delta) value. A By constructor 530 receives a delta value,starts an animation at a base value, and proceeds to change the basevalue by the amount specified by the delta value during the course ofthe animation cycle. A From-by constructor 540 receives as its input astarting “From” value and proceeds to change the initial “From” value bya passed delta value during the animation cycle. Having described abasic set of constructors for animation objects, it is noted that thepresent invention contemplates a wide variety of animation behaviors(and corresponding constructors)—including composites/combinations ofthe aforementioned behaviors.

[0115] Having described an exemplary animation class structure,attention is now directed to the container of the animation objects, theanimation collection classes 224. Turning to FIG. 6, an exemplarystructure for an animation collection class is depicted. Animationcollection objects maintain a list of animation objects instantiatedfrom animation classes 224. Turning first to a set of methods 600supported by the animation collection classes, a GetUniqueInstancemethod returns an animation collection instance with a default parenttimeline corresponding to a passed timeline identification. Theanimation collection class also supports an interface for setting aDefaultParentTimeline property on an animation collection class. In anexemplary embodiment of the invention, the property system 220 calls theGetUniqueInstance method to obtain a copy of a particular animationcollection for a dynamic animation collection object. The animationcollection object contains a list of animation objects. A builderfunction/entity adds animation objects to the created animationcollection instance. The animation objects within the animationcollection are indexed and referenced/accessed by specifying aparticular position within the list (as in an array).

[0116] A GetValue method takes as an input a base value, of a certaintype, and returns another value of the same type as the input basevalue. The value of the output depends both on the input (base value)and on the internal state of the modifier (e.g., animationobject/collection) to which it is passed. In particular, this means thatcalling GetValue more than once with the same input is not guaranteed toreturn the same output, and in fact it is expected to change during thecourse of an animation sequence. In the case of the animation collectionclass, the GetValue method provides a passed base value to the firstanimation object in its collection. The output of the first animationobject becomes the input base value to a next animation object (ifpresent) in the animation collection. This process repeats until thelast animation object in the animation collection has computed anoutput. The GetValue method returns the output value provided by thelast animation object within the pipeline of animation objects withinthe animation collection.

[0117] The animation collection class also includes a set of properties610. An IsChanging property and IsOverridingBaseValue property aresimilar to the correspondingly named properties on animation objects.However, in the case of an animation collection class, the propertiesare merged such that if any one of the animation object's correspondingproperties returns “True,” then the corresponding property on theanimation collection returns “True.” The Animations(array) propertymaintains a list of the animation objects within the animationcollection.

[0118] The animation collection also supports a set of events 620. TheChanged events coalesce and report the corresponding events, describedherein above, fired from the constituent animation objects of theanimation collection.

[0119] Turning now to FIG. 7, a set of methods and properties areidentified for the dynamic animation collection class 226. The set ofmethods 700 includes a dynamic animation collection constructor method.The dynamic animation collection constructor method receives as input,an element reference (on the element tree 202), a dynamic property onthe element, and an animation collection instance, the constructorreturns a dynamic animation collection object that operates as aninterface between the timeline induced changes to animation objectswithin the passed animation collection object, and the dynamic propertyon the element contained in the element tree 202.

[0120] An interface on the dynamic animation collection object supportssetting/getting the animation collection object with which the dynamicanimation collection object is associated. A SetDefaultParentTimelinemethod repairs timeline connections in the event that the element, towhich the dynamic animation collection object is attached, is relocatedin the element tree 202 or the timing for the element is otherwisechanged.

[0121] A GetValue method-returns the current value for the element'sanimated property (provided by the animation collection to which thedynamic animation collection is attached).

[0122] An OnChanged method is called when the progress of any animationobject within the animation collection has changed. When invoked, theOnChanged method causes an invalidation of the dynamic property. Thisin-turn invokes the re-rendering of affected elements.

[0123] Turning to the properties 710, an OriginalDynamicPropertyproperty returns a reference to the dynamic property with which thedynamic animation collection is associated. An Element property returnsthe element with which the dynamic animation collection is associated.The IsOveridingBaseValue returns a value based upon a call to thecorrespondingly named property on the animation collection with which itis associated.

[0124] Having described an animation architecture, using the describedarchitecture to animate properties on elements by giving themtime-varying values is described by way of example. In general, everyanimated resource, method or object includes an interface enablingnotification of the entity's animation capabilities, its default parenttimeline, whether it has changed, a current value of the object, andwhether the entity is changing. By way of particular example, theinterface of an animatable entity includes a DoesChange property thatreturns True if the object may vary with time. In general, theDoesChange property is true if the object is holding any animationcollections. A DefaultParentTimeline property returns a reference to atimeline that is the parent of any auto-parented timelines. If theDefaultParentTimeline property is set, then any auto-parented timelinesare re-parented, but a new clone is not created either for the timelinesor for this animatable object. An IsChanging property returns True ifany of the animations in an animatable object are changing. AnIsOverridingBaseValue property returns True if any timeline of theanimatable object is active or in a fill period. A Changed event israised whenever the animatable entity's value changes.

[0125] In addition, the animatable entity includes a CurrentValue methodthat returns an object that is used as the value of the property. Thevalue is the instantaneous value of the object, but it does not changeonce it is set. A GetUniqueInstance method, specifying a particulartimeline, returns an object that can be used as the value of a property.If the object refers to any auto-parented timelines, the instancereturned has those timelines parented to the specified default parenttimeline.

[0126] An animatable entity also specifies for every animatableproperty, a corresponding reference to an animation collection type tofacilitate creation of a dynamic animation collection by the propertysystem. In an embodiment of the invention, animation collections areused rather than basic animation objects since such usage would precludeanimation composition.

[0127] Resources are animated by adding animation collections toindividual properties. The following example shows how to create aSolidColorBrush with an animate color.  ColorAnimationBuilderanimBuilder = new ColorAnimationBuilder();  animBuilder.From = newColor(1.0f, 0.0f, 0.0f, 0.0f);  animBuilder.Begin = new Time(0); animBuilder.To = new Color(1.0f, 1.0f, 0.0f, 0.0f); animBuilder.Duration = new Time(1000);  animBuilder.AutoReverse = true; animBuilder.RepeatDuration = Time.Indefinite;  SolidColorBrushBuilderbrushBuilder = new SolidColorBrushBuilder();  brushBuilder.Color = newColor(1.0f, 0.0f, 0.0f, 0.0f);  brushBuilder.ColorAnimations =animBuilder.ToColorAnimation();  SolidColorBrush animationBrush =brushBuilder.ToBrush();

[0128] Animate resources can be used in rendering operations or asvalues for element properties. A rendering operation is animated, by wayof example, by adding animation collections to drawing context methodcalls, or by using animate resources. The following example shows how topush an animated opacity value into a drawing context. FloatAnimationBuilder animBuilder = new FloatAnimationBuilder(); animBuilder.From = 0.0f;  animBuilder.Begin = Time.Immediately; animBuilder.To = 1.0f;  animBuilder.Duration = new Time(1000); animBuilder.Fill = TimeFill.Freeze;  nyDrawingContext.PushOpacity(0.0f,animBuilder.ToFloatAnimation());

[0129] Elements can be animated by adding animation collections toElement properties. The following example shows how to animate th ewidth of a button in C sharp.  BoxUnitAnimationBuilder animBuilder = newBoxUnitAnimationBuilder();  animBuilder.From = new BoxUnit(50); animBuilder.Begin = Time.Immediately;  animBuilder.To = newBoxUnit(100);  animBuilder.Duration = new.Time(1000); animBuilder.Acceleration = 0.2;  animBuilder.Deceleration = 0.2; animBuilder.Fill = TimeFill.Freeze;  myButton.Width = new BoxUnit(50); myButton.WidthAnimations = animBuilder.ToBoxUnitAnimation();

[0130] The following shows the same example in XAML <ButtonID=“myButton” Width=“50”>  <Button Width>   <BoxUnitAnimation   From=“50”    Begin=“Immediately”    To=“100”    Duration=“1”   Acceleration=“0.2”    Deceleration=“0.2”    Fill=“Freeze”   /> </Button.Width> </Button>

[0131] Whenever an animation (or an animated resource) is used, theanimation (or resource) is cloned to provide the destination with aunique, independently controllable timeline. A consequence of thisparticular way of implementing animation on a property is that theoriginal animation is never part of a visual scene, and therefore itdoesn't respond to control calls through an animation object's timinginterface. To achieve this effect, the calling code must first use ananimation and then read the animation back. The value that is read backcan then be cached and used for timing control. The following exampleshows a pattern that code intending to control animations follows: private FloatAnimation myOpacityAnimation;  public void Initialize()  {  FloatAnumationBuilder animBuilder = new FloatAnimationBuilder();   //Set the Begin property to Idefinite because we want to start   // thisanimation interactively, not automatically   animBuilder.Begin =Time.Indefinitely;   animBuilder.From = 1.0f; // Fully opaque  animBuilder.Duration '2 new Time(500); // half a second  animBuilder.To = 0.5f; // Half transparent   animBuilder.AutoReverse =true;   // Create the animation   FloatAnimation animationanimBuilder.ToFloatAnimation();   //Animate the opacity of some elementwe own   mtElement.Opacity = 1.0f;   myElement.OpacityAnimations '2animation;   // ERROR: The following line doesn't have the intendedresult:   // myOpacityAnimation '2 animation;   //   .. This line cachesan animation “template”, not the actual animation   // that controls theopacity of the element.   // This caches the right animation -- the onethat is actually in use.   myOpacityAnimation =(FloatAnimation)myElement.OpacityAnimations[0];  }  public voidOnSomeEvent ()  {   // Whenever we detect some event, “blink” theelement   myOpacityAnimation.BeginIn(0);  }

[0132] It will be appreciated by those skilled in the art that a newexemplary platform and exemplary interfaces, classes and structuresincorporated therein have been described for attaching and executinganimation behaviors to graphical display elements within a computingenvironment including graphical output devices such as a graphical userinterface display. In view of the many possible environments to whichthe principles of this invention may be applied and the flexibility ofdesigning and carrying out the above-described animation architecture,it should be recognized that the embodiments described herein are meantto be illustrative and should not be taken as limited the scope ofinvention. Those skilled in the art to which the present inventionapplies with appreciate that the illustratively presented embodimentscan be modified in arrangement and detail without departing from thespirit of the invention. Therefore, the invention as described hereincontemplates all such embodiments as may come within the scope of thefollowing claims and equivalents thereof.

What is claimed is:
 1. A graphical display animation system supportingtimed modification of element property values, the graphical displayanimation system comprising: a display structure for maintaining a setof elements, wherein an element includes a variable property valueaffecting a display characteristic of the element; a property system formaintaining properties associated with elements maintained by thedisplay structure, including dynamic properties that are capable ofchanging over time; and animation classes, from which animation objectsare instantiated, wherein the animation object instances provide timevarying values affecting values assigned to the dynamic properties. 2.The graphical display animation system of claim 1 further comprising: adynamic animation class, that associates one or more animation objectswith a dynamic property of an element within the display structure. 3.The graphical display animation system of claim 1 further comprising: ananimation collection class, for grouping a set of animation classobjects, wherein an instance of the animation collection class providesa composed output value by applying the set of animation class objectsto a base value.
 4. The graphical display animation system of claim 1wherein the animation classes each specify an internal timeline.
 5. Thegraphical display animation system of claim 4 wherein animation objectinstances are attached to a parent timeline that provides a context fora timing sequence defined by the internal timeline.
 6. The graphicaldisplay animation system of claim 5 wherein the parent timeline isspecified by a container for the animation object instances.
 7. Thegraphical display animation system of claim 1 wherein ones of theanimation classes are associated with a particular data type for whichthey render a time variable value.
 8. The graphical display animationsystem of claim 7 wherein an animation class of the animation classesprovides a floating point value.
 9. The graphical display animationsystem of claim 7 wherein an animation class of the animation classesprovides dimensions for a presenter box.
 10. The graphical displayanimation system of claim 7 wherein an animation class of the animationclasses provides the top, left position of a rectangle.
 11. Thegraphical display animation system of claim 7 wherein an animation classof the animation classes provides a time-changing color value.
 12. Thegraphical display animation system of claim 7 wherein an animation classof the animation classes provides a Boolean value.
 13. A method foranimating display elements in a graphical display system including adisplay structure for maintaining a set of runtime display elementsgenerated by an executing program and a property system for managingproperties associated with the display elements, and wherein animatingones of the display element is achieved by modifying display elementproperty values in response to a passage of time, the method comprising:creating a graphical display element including a modifiable property;defining an animation behavior assignable to the modifiable property;associating, in accordance with requests from a program at runtime, theanimation behavior with the modifiable property of the element; andproviding a sequence of time-varying values to the modifiable propertyin accordance with the animation behavior.
 14. The method of claim 13further comprising providing a set of animation classes, wherein eachanimation class defines an animation behavior.
 15. The method of claim13 wherein the set of animation classes specify an animation type,wherein an animation type corresponds to a type of data processed byinstances of an animation class.
 16. The method of claim 13 wherein theproviding step is facilitated by an animation object instantiated froman animation class embodying the animation behavior.
 17. The method ofclaim 13 wherein the defining an animation behavior step comprisesgrouping a set of animation class instances within an animationcollection class, wherein an instance of the animation collection classprovides a composed output value by applying the set of animation classinstances to a base value.
 18. The method of claim 13 wherein theassociating step comprises instantiating a dynamic animation class thatattaches one or more animation objects to the modifiable property on theelement.
 19. The method of claim 13 wherein timing for the progressionof the sequence of time-varying values is specified in accordance with atiming tree node associated with one or more animation objects definingthe animation behavior.
 20. The method of claim 13 further comprisingattaching a parent timeline to an animation object thereby providing aglobal timing context for a local timing sequence defined by an internaltimeline.
 21. The method of claim 20 wherein the parent timeline of theanimation object is specified by a container for a collection ofanimation object instances.
 22. The method of claim 13 wherein theproviding a sequence of time-varying values step comprises applyingmultiple times, over an active animation period, a current time and abase property value to an animation value generator embodying theanimation behavior, to render a current value for the modifiableproperty; and generating an updated layout in accordance with thecurrent value for the modifiable property.
 23. A method for applying ananimation behavior to an element property maintained by a propertysystem to implement sequential modifications to the element propertyvalue over the course of time, said method comprising: instantiatinganimation object instances from animation object classes specifyingbasic animation behaviors; instantiating an animation collection objectfrom an animation collection class specifying a list of constituentanimation objects; and instantiating a dynamic animation collection froman animation collection class that associates the animation collectionobject with the element property maintained by the property system. 24.The method of claim 23 further comprising assigning parent timelines toinstances of the animation object classes.
 25. The method of claim 23further comprising locking the properties of animation object instances.26. The method of claim 23 further comprising locking the properties ofanimation collection object instances.
 27. The method of claim 23further comprising: applying a current time and a base property value tothe constituent animation objects of the animation collection object torender a current property value for the element property; and generatingan updated layout in accordance with the current property value for theelement property.
 28. A computer-readable medium including computerexecutable instructions for providing a graphical display animationsystem supporting timed modification of element property values, thegraphical display animation system comprising: a display structure formaintaining a set of elements, wherein an element includes a variableproperty value affecting a display characteristic of the element; aproperty system for maintaining properties associated with elementsmaintained by the display structure, including dynamic properties thatare capable of changing over time; and animation classes, from whichanimation objects are instantiated, wherein the animation objectinstances provide time varying values affecting values assigned to thedynamic properties.
 29. The computer-readable medium of claim 28 whereinthe graphical display animation system further comprises: a dynamicanimation class, that associates one or more animation objects with adynamic property of an element within the display structure.
 30. Thecomputer-readable medium of claim 28 wherein the graphical displayanimation system further comprises: an animation collection class, forgrouping a set of animation class objects, wherein an instance of theanimation collection class provides a composed output value by applyingthe set of animation class objects to a base value.
 31. Thecomputer-readable medium of claim 28 wherein the animation classes eachspecify an internal timeline.
 32. The computer-readable medium of claim31 wherein animation object instances are attached to a parent timelinethat provides a context for a timing sequence defined by the internaltimeline.
 33. The computer-readable medium of claim 32 wherein theparent timeline is specified by a container for the animation objectinstances.
 34. The computer-readable medium of claim 28 wherein ones ofthe animation classes are associated with a particular data type forwhich they render a time variable value.
 35. The computer-readablemedium of claim 34 wherein an animation class of the animation classesprovides a floating point value.
 36. The computer-readable medium ofclaim 34 wherein an animation class of the animation classes providesdimensions for a presenter box.
 37. The computer-readable medium ofclaim 34 wherein an animation class of the animation classes providesthe top, left position of a rectangle.
 38. The computer-readable mediumof claim 34 wherein an animation class of the animation classes providesa time-changing color value.
 39. The computer-readable medium of claim34 wherein an animation class of the animation classes provides aBoolean value.